iflib:
Add internal tracking of smp startup status to reliably figure out
what methods are to be used to get gtaskqueue up and running.
e1000:
Calculating this pointer gives undefined behaviour when (last == -1)
(it is before the buffer). The pointer is always followed. Panics
occurred when it points to an unmapped page. Otherwise, the pointed-to
garbage tends to not have the E1000_TXD_STAT_DD bit set in it, so in the
broken case the loop was usually null and the function just returned, and
this was acidentally correct.
Submitted by: bde
Reviewed by: Matt Macy <mmacy@nextbsd.org>